Ribosomes function is primarily limited to protein synthesis in the cells.
But they also act as targets for few drugs in the treatment of diseases.
Ribosomes are complex structures having two sub units.
One subunit is larger one while the other one is smaller in size.
Chemically they are a combination of ribonucleic acid with proteins.
Ribosomes are present mostly on the endoplasmic reticulum. They help in
- Provide scaffolding for assembly of molecules involved in protein synthesis
- Bind to mRNA and help to initiate translation
- They act as target for antibiotics in treatment of bacterial infections.
- They help in synthesis of few cell organelles like the lysosomes.
Before we go into more details it is necessary to have clear idea about ribosomes.
Ribosome structure: Ribosomes are present a twp subunits. A larger subunit and smaller subunit.
By difference, there are two types as 70s ribosome and 80S ribosome. The 70S form is present in prokaryotic cells and 80S ribosome is present in eukaryotic cells.
The 70S ribosomes consists of two subunits as 30S ribosomal sub-unit and 50s ribosomal subunit.
While the 80S ribosome consists of tow subunits as 40S and 60S subunit.
Both the ribosome types have similar functions of protein synthesis.
However due to minor differences in their chemistry and structure, they have differential susceptibility to drugs.
70 ribosome is present in bacteria and hence, when there is bacterial infection, antibiotics are given.
These antibiotics act on 70S ribosome sparing the 80S ribosome of the animal. The function of 70S ribosome is hindered and thereby the protein synthesis. This leads to the inhibition in the growth of bacteria. Since, the 80S ribosome is not susceptible to the antibiotics; humans are not affected by the drug. Thus antibiotics are selective to bacterial cells and not the human cells. However, since both types of ribosome have large similarity, at doses of antibiotics, the 80S type is also susceptible. Hence, at higher doses there are side effects due to antibiotics.
Functions of ribosomes in detail:
- Protein synthesis: As discussed before, ribosomes play a key role in protein synthesis. When the mRNA formed in the nucleus comes out into cytoplasm, it sits on the ribosomes present on rough endoplasmic reticulum. The ribosomes then help in initiating the translation. The polypeptide chain is formed by addition of aminoacids by the tRNA.
- Cell organelle synthesis: Few cell organelles like the lysosomes are specifically formed by the ribosomes. These ribosomes have diverse function in the cell.
- Antibiotics susceptibility: This is the advantage provided by the ribosome to the enemy. Few fungi produce antibiotics to prevent growth of bacteria around them. The same technique is exploited by humans to control the bacterial infections in health care. The antibiotics which target protein synthesis specifically bind to the 70S ribosome in the bacteria and kill them. Thus the humans get free of bacterial diseases when these antibiotics are taken.